This invention relates to distributed antenna systems, more particularly to a monitoring system and method for a distributed antenna system.
Distributed antenna systems (DAS) are known in the art and are typically employed to provide in-building coverage, but more recently are also used to provide area coverage outside of buildings. DAS may be passive or active. A passive DAS comprises a central or base transceiver station linked by a radio frequency (RF) signal transmission network comprising RF transmission lines (coaxial or other) to a plurality of distributed antenna devices (DAD) distributed through the area to be covered with power diverted according to some propagation plan to each DAD, such that adequate coverage is ensured throughout the building or area for which the DAS is installed.
An active DAS is similar, but in these systems the RF signals are modulated up to convert them to optical fibre frequencies. Optical fibers are then used to distribute the resulting signals to a point close to the DAD. An optic-to-radio converter unit is used to convert the signals back to their original RF band. The optic-to-radio convertor is coupled using RF transmission lines which provide the last mile to one or more DAD's, which provide coverage to sub-areas of the area covered by the DAS. Other active DAS systems may involve bi-directional amplifiers and/or frequency convertors in between the central transceiver and the DADs.
A DAS may employ between a few to many hundreds of DAD's to provide coverage throughout the area. These DAD's or the signal transmission network and intermediate devices used to link these DAD's to the base transceiver station may fail or degrade over time. Currently such faults are difficult to detect or monitor. One known solution is to use regular “walk tests” to measure network coverage throughout the coverage area, but these are time consuming, costly and faults are detected well after they had occurred.
In U.S. Pat. No. 8,254,848 there is disclosed another solution which comprises a plurality of statically deployed monitoring devices. The monitoring devices are remote from the DAD's being monitored and test results are reported to a central and remote collection component directly or indirectly through other monitoring devices having an Ethernet connection. This solution may be unnecessarily costly. Furthermore, due to the separation between DAD's and the monitoring devices, individual DAD's and branches in the network may be difficult to pinpoint. Hence, the solution may not be suitable for at least some applications.